This invention relates to an image processing apparatus and method and, more particularly, to an image processing apparatus and method for displaying image data on a device, such as an FLC (ferrodielectric liquid-crystal device) having a comparatively small number of reproducible tones.
CRT monitors used in modern computers and the like are analog devices capable of expressing half-tone colors beautifully. Devices of this kind are capable of displaying motion pictures in excellent fashion in recent multimedia applications.
Binary-image display devices such as FLCs extract a digital signal from a computer and subject the signal to appropriate binarization processing, thereby making possible highly attractive pseudo-half-tone expression.
In a configuration in which an FLC is connected to a computer, it is required that the connection be made via an analog interface having compatibility with an existing analog CRT monitor. However, quantization noise is produced by the A/D converter circuit, and the size and position of the noise change between frames.
Consequently, when binarization is performed by the error diffusion (ED) method, the state of error diffusion varies temporally between frames, as a result of which the pattern of noise intrinsic to the ED circuitry darts about on the display screen over multiple frame sequence. This results in an annoying and highly unattractive display. In an effort to solve this problem, the conventional practice is to perform binarization using the dither method, without relying upon the ED method. However, a drawback with the dither method is that slender portions of the image tend to blur.
Thus, there is need for development of a method in which noise will not appear in spite of using the ED method, which is held to be the best method for producing still pictures.